Xiyue Wang, the Princeton University graduate student and American citizen who has been in prison in Iran since the summer of 2016, has been moved from the general prison population to another unit called Ward 7 that is run by Iran’s intelligence agency, according to his wife.

His wife, Hua Qu, said when he was previously in the unit, he was assaulted by a Taliban inmate and repeatedly harassed by other inmates who had previously been imprisoned in U.S. detention centers at Guantanamo Bay, Cuba and Bagram Airbase, Afghanistan.

“After losing contact with Wang for 30 hours, he called me minutes ago and told me that the Intelligence has put him in ward 7 with a Taliban who was imprisoned at Bagram Airbase, Afghanistan for years,” Hua Qu wrote in an update to supporters. “This Taliban (person) is the guy who used to badly beat Wang when both of them were in political prison 209. In front of the prison head, the Taliban threatened to kill Wang as soon as he met Wang again yesterday.”

Hua Qu is worried about her husband’s safety and has asked supporters to contact their senators and representatives to call on them to advocate for Wang’s release.

“I am horrified and deeply concerned. Wang’s life is in imminent danger,” she wrote. “The Iranians are doing all of these to make my husband suffer physically and mentally, and in return press the US government.”

According to the Iranian government, Wang was a spy who allegedly scanned about 4,500 pages of digital documents, paid thousands of dollars to access archives, and sought access to restricted areas of libraries.

Princeton University has said that Wang was not involved in any political activities or connected to any government agencies. He was a scholar conducting historical research. He went to Iran as a doctoral candidate in the history department, and was studying Eurasian languages and regional governance practices in the late 19th and early 20th centuries for his dissertation. In connection with his doctoral research, he traveled to Iran to study Farsi and to examine historical documents from the late 19th and early 20th centuries. He described his research plans in advance to the Iranian authorities and the libraries and archives he planned to visit, and he only sought access to materials that he needed for his dissertation.